Hi there,
It must bee quite worrying to see them like that. Have you bred these dogs before?
Where they still suckling from mum or not taking anything at all?
What are you feeding them and what routine? are you mixing food with a milk substitute? is it a puppy specific diet?
Obviously at this age their stomachs are quite sensitive and still quite small so you will need to be carefull what you give them, the food should be easily digestable and given in small meals during the day, best mixed with a puppy milk substitute, cows milk should not be used as this is quite hard for them to digest at this age and could cause problems.
How is the first puppy now? is it eating? and keeping food down.
The Vet has ruled out anything contagious and all bloods were normal.
Is the puppy retching or just regurgitating the food?
Its difficult to say what it could be with out seeing the puppy its self, but there are hereditary and congential conditions that make the Oephagus stricture i.e the ipe that the food travels down in to the stomach cab be narrowed stopping food from going in to the stomach, so after afew mins the food is regurgiated back up.
In this case the puppy should be fed so that his head is raised and kept that wasy for at least 20 mins.
If they are still not eating or drinking i would return them to the vets asap, it is surprizing how quickly a little pup can become dehydrated.
Regards
Selena
VN